The demand for high-voltage insulated-gate bipolar transistor (IGBT) devices for automotive electronics applications has increased dramatically, particularly for such applications as coil drivers for ignition systems and motor drivers for electric vehicles. Accompanying this increased demand is a desire for "smart" IGBT devices, i.e., IGBT devices that are monolithically integrated with control circuitry to provide self-protection from over-temperature (OT), over-voltage (OV) and over-current (OC) conditions. However, full integration of an IGBT device with its control circuitry is complicated by the high voltages at which IGBT devices must operate, often about 400 to 1400 volts, and because the level of minority carriers present with IGBT devices would interfere with the low-voltage control circuitry.
Several techniques have been suggested by which various electronic power devices can be integrated with suitable control circuitry. For example, relatively low-voltage (40 to 100 volts) vertical DMOS (double-diffused metal-oxide semiconductor) devices are commercially available that rely on junction-isolation (JI) to provide electrical insulation for their control circuitry. However, junction-isolation cannot adequately protect control circuitry from the minority carriers inherent with IGBT devices. Silicon-on-insulator (SOI) technologies, such as wafer-bonding and separation by implantation of oxygen (SIMOX), have been employed in the fabrication of DMOS devices to achieve dielectric-isolation (DI), a viable isolation technique for use with high-voltage IGBT devices. However, such techniques have proven to be costly and/or yield devices characterized by inadequate performance or reliability. The use of polysilicon thin-film transistors for the control circuitry of DMOS devices has also enabled the implementation of dielectric-isolation. However, a shortcoming of this approach is that the performance of polysilicon transistors is inferior to equivalent single-crystal devices. Similar efforts to achieve dielectric-isolation with polysilicon structures for high-voltage IGBT devices have generally incurred relatively high processing costs.
In view of the above, it would be desirable if a process were available that would enable the monolithic integration of an IGBT device with suitable control circuitry, in which the resulting device is characterized by effective isolation of the control circuitry at high operating voltages, high performance, and relatively low processing costs.